1. Field of Invention
The present invention relates to a fixed abrasive wire and, more particularly, to a method and apparatus for making a fixed abrasive wire.
2. Related Prior Art
The photoelectrical industry has been booming recently. There is a growing need for precious, hard and brittle materials such as silicon wafers, sapphire and agate. Silicon wafers are essential for the development of integrated circuits. The silicon wafers are sliced into dies for integrated circuits. During the slicing of the silicon wafers, there is always loss of materials, and the slicing of the wafers is hence expensive. There is a need for an excellent wafer-slicing process.
A wafer can be sliced with a sawing wire. The sawing wire may be operated in a free abrasive manner or a fixed abrasive manner. In the free abrasive manner, a wire is used with abrasive paste for slicing. The efficiency and precision of the free abrasive operation are low, and the consumption of the abrasive paste pollutes the environment.
In the fixed abrasive manner, abrasive grains are fixed to a wire by adhesive, electroplating or electro-less plating for example. The efficiency and precision of the fixed abrasive operation are high, and there is no waste related to the disposal of any abrasive paste. Therefore, the fixed abrasive operation is popular.
A method for making a fixed abrasive wire by electroplating was devised by Ken-Ichi Ishikawa in 1994. In the method, a tank that contains abrasive grains such as diamond grains is used as a composite electroplating tank. A wall of the tank is made with apertures of a diameter of 10 mm and coated with a Teflon film that is 3 μm thick. The abrasive grains are restrained in the tank by the Teflon film while nickel-based electroplating liquid is allowed to flow through the tank. A wire electrically connected to the cathode of a power supply is buried in the abrasive grains and electroplated in the electroplating liquid so that some of the abrasive grains can be fixed to the wire. However, the area of the contact of the electroplating liquid with the wire is small, and the electroplating takes a long time. Furthermore, it is difficult to control the amount and distribution of the abrasive grains fixed to the wire.
In a typical method for making a fixed abrasive wire by adhesive, abrasive grains are fixed to a wire by adhesive that includes copper, tin or titanium in a high-temperature chamber filled with inert gas or a high-temperature vacuum chamber. The control over the abrasive grains is good. However, the wire and abrasive grains could be damaged in the high-temperature chamber, and mechanical properties of the resultant fixed abrasive wire are jeopardized.
The foregoing methods for making fixed abrasive wires are not without problems. Therefore, the present invention is intended to obviate or at least alleviate the problems encountered in prior art.